Hairlike fuzz on rock.

[TWYOUNG]

Can anyone ID these fine white hairlike growths on my rock? It is more prevalent in shaded or possibly areas inaccessible to my cuc. Almost looks like fur.

 

[Formulator]

I have them in my tank in some cryptic spaces in caves and in my sump also. They have been there for many years without causing a problem. I am not positive what they are but have narrowed down to some kind of sponge or bryozoan. They could also be tube worms or feather dusters if they are crunchy.

 

[ISpeakForTheSeas]

I do see some sponge in the pics, but the hair-like things are probably either micro feather duster worms or possibly hydroids. If you can get closer pics of them (given the size, a magnifying tool like a microscope or a jeweler's loupe may be necessary)/of anything that pops out of them, then I may be able to give a proper ID on at least the kind of organism they are.